Metamaterials Let Smaller Antennas Perform Like Much Larger Ones

The world of ever-shrinking electronics and communication devices could benefit from a recent development at the National Institute of Science and Technology, Gaithersburg, Md.: pint-sized antennas that perform as well as much larger versions. In fact, the new so-called Z antennas radiate as much as 95% of their input signal yet defy normal performance parameters. For example, standard antennas must be at least half the size of the signal wavelength to operate efficiently, but Z versions can be as small as one-fiftieth of a wavelength. And further research could shrink that figure.

The key to Z antennas is using metamaterial, a man-made material or device that affects electromagnetic energy. For example, in a prototype antenna, NIST engineers added a Z-shaped strip of copper with an inductor — the metamaterial — to a copper square measuring 30 mm on a side, extremely small for an antenna. The metamaterial makes the antenna behave as if it were larger by storing and reradiating electromagnetic energy. If a conventional antenna is too small to efficiently handle the wavelength of interest, the signal gets reflected back to the source. To boost the efficiency of smaller conventional antennas, engineers must add bulky “matching network” components. Besides being smaller than current antennas, Z antennas are more frequency agile, meaning they could be tuned to work at any frequency on the fly.